The conventional Analog Front-End (AFE) circuitry, also known as the input network, of a DVD/CD drive or other devices is tailored for only one, or at most several very similar Optical Pick-Up Units (OPUs) or Photo-Detector Integrated Circuits (PDICs). It is nontrivial to support different varieties of OPUs or PDICs, not to mention that the challenge to support both voltage-mode and current-mode OPUs or PDICs is high. A voltage-mode OPU (or PDIC) converts the optical signals read back from the discs to electrical signals in the voltage format and delivers the signals to the AFE of the DVD/CD system chip. Current-mode OPUs (or PDICs), on the other hand, deliver information in terms of current to the AFE of DVD/CD system chip.
Traditional AFEs of the DVD/CD systems tend to consume excessive amounts of power since the signal is single-ended and is prone to the strong influence of the noise and crosstalk generated both on the printed circuit board (PCB) and on the chip. Also, the common-mode level of the signal can drift substantially due to temperature variation. This hinders the effectiveness of the calibration and can demand multiple calibrations during normal operations.